Differences in aerosol flow rates between disposable and reusable atomizers used for airway topicalization: implications
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Differences in aerosol flow rates between disposable and reusable atomizers used for airway topicalization: implications for local anesthetic toxicity Haotian Wang, MD . R. Zachary Ford, BSc . Andrew D. Milne, MD, MSc
Received: 5 September 2020 / Revised: 24 October 2020 / Accepted: 28 October 2020 Ó Canadian Anesthesiologists’ Society 2020
To the Editor, Awake flexible bronchoscopic intubation is one method used to manage a patient with a difficult airway.1,2 Topicalization of the airway with local anesthetic (LA) prior to awake tracheal intubation is important to blunt the gag and cough reflexes, thus minimizing patient discomfort. Modalities of LA delivery to the airway include liquid gargles, topical gels or pastes, targeted nerve injections, and atomization for inhalation.1,3 Careful consideration should be given to the cumulative LA dose administered with these modalities to reduce the risk of potential LA systemic toxicity.1,4 Our institution recently changed from reusable DeVilbiss atomizers (Model 15, DeVilbiss Healthcare, Somerset, PA, USA) to disposable atomizers (EZ-100 and EZ-100m, Alcove Medical, Lehi, UT, USA) to prevent cross-contamination between patients. The purpose of this study was to compare the simulated LA delivery flow rates between these atomizer devices. Institutional ethics approval was not required for this bench-top equipment study. Standard E-cylinder oxygen
Presented in part at the Difficult Airway Society Meeting, London, England, 2017. H. Wang, MD (&) R. Z. Ford, BSc Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada e-mail: [email protected] A. D. Milne, MD, MSc Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
tanks were used as the carrying gas for atomization. Full tanks were used and replaced when half empty. Atomizer chambers were filled to their nominal capacity (DeVilbiss 20 mL, EZ-100m 15 mL, and EZ-100 50 mL) using a standard medical grade syringe. The time to empty each device under continuous discharge was recorded using a handheld stopwatch. To allow direct comparison between devices with different filling volumes, the aerosol flow rate was calculated (flow = volume/time). To determine the effects of fluid type on delivery rate, a pilot trial was performed for each oxygen flow rate with liquid lidocaine (LidodanÒ 4%, Odan Laboratories Ltd, Montre´al, QC, Canada) and then sterile water. There was no appreciable difference between the flow rates for 4% lidocaine and sterile water. Subsequently, five repeated trials were performed with six devices of each model type at seven different oxygen flow rates (4–25 Lmin-1) using sterile water (i.e., simulated LA). The accuracy of portable oxygen tank flow meter settings were tested using a sample of six full oxygen tanks using a Puritan BennettTM ventilator flow tester. Significant differences in the aerosol
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